In the field of the production of materials based on resin reinforced by a fibrous structure, which materials in the description which follows will be referred to by the expression "composite materials", apart from conventional fibres such as glass fibres which have been employed for decades, it has now been proposed to employ so-called "high mechanical performance" fibres, especially aramid fibres, carbon fibres etc.
In general, such textile reinforcements based on high mechanical performance fibres are in the form of balanced or unbalanced fabrics. A disadvantage of these fabrics, however, is the fact that they are very easily deformed, and, when the composite materials are being produced, this results in a disorientation of the fibres and consequently in inhomogeneous characteristics.
Furthermore, it has been proposed for a long time to produce so-called mixed reinforcing fabrics, as follows from FR-A-2,034,787, in order to combine the specific properties of substances of different kinds. Thus, in the abovementioned document a fabric is produced, comprising, as warp, strands of glass fibres and of carbon fibres, alternating and bound together by binding wefts.
However, with a solution of this kind it is difficult to obtain thick reinforcements.
There are also known mixed composites consisting of needled felts based on a mixture of fibres, as follows from FR-A-2,248,937. While such felts have the advantageous characteristics of being easily formed, they nevertheless have the disadvantage of not imparting high strengths in the lengthwise, transverse or other direction.
There has now been found, and this is what forms the subject of the present invention, an improvement introduced into the textile reinforcements in the form of fabrics based on aramid fibres (or any other similar material) which not only makes it possible to preserve the characteristics of the said fibres in the composite material, but also improves the adhesiveness properties of the said substance to the resin, more particularly when a polyester resin is involved, and which removes any risk of delamination which might occur.